Endoglucanases (EC no. 3.2.1.4) constitute a group of hydrolases, which catalyse endo hydrolysis of 1,4-.beta.-D-glycosidic linkages in cellulose, cellulose derivatives (such as carboxy methyl cellulose and hydroxy ethyl cellulose) lichenin, .beta.-1,4 bonds in mixed .beta.-1,3 glucans such as cereal .beta.-D-glucans or xyloglucans and other plant material containing cellulosic parts. The authorized name is endo-1,4-.beta.-D-glucan 4-glucano hydrolase, but the abbreviated term endoglucanase is used in the present specification. Reference can be made to R. F. Gould, "Cellulases and their Application", Advances in Chemistry Series 55, American Chemical Society (1969), T. M. Wood, "Properties and Mode of Action of Cellulases", in Biotechnology and Bioengineering Symposium, no. 5, John Wiley, 111-137 (1975), Y. -H. Lee and L. T. Fan, "Properties and Mode of Action of Cellulose", Advances in Biochemical engineering 17, 101-129 (1980), J. Goksyr and J. Eriksen, "Cellulases" in A. H. Rouse, Microbial Enzymes and Bioconversions, Academic Press, 283-330 (1980), T. -M. Enveri, "Microbial Cellulases" in W. M. Fogarty, Microbial Enzymes and Biotechnology, Applied Science Publishers, 183-224 (1983).
Endoglucanases have been found to be produced by various types of organisms such as plants and microorganisms, and endoglucanases of a wide variety of specificities have been identified. For instance, xyloglucan specific endoglucanases have been identified in various plants, cf the disclosure of Fry et al. (1992), Nishitani and Tominaga (1992), Hayashi et al. (1984), McDougall and Fry (1991), and WO 93/17101. All of these enzymes have been found to have transferase activity (as defined e.g. by Fry et al., 1992 and Nishitani et al., 1992) and are not, accordingly, classified as a real endoglucanase. Hitherto, xyloglucan specific endoglucanases have not been identified in microorganisms.
Microbial endoglucanases have been described by Beldman et al., 1985 (Trichoderma viride) and in WO 93/20193 (Aspergillus aculeatus), the latter reference being published only after the priority dates of the present invention. Furthermore, Sharma et al., 1991, Ooi, et al., 1990, and Gilkes et al. 1991 describe microbial endoglucanases.
Endoglucanases may advantageously be used for the degradation of cellulose components present in plant cell walls and bacterial polysaccharides. Endoglucanases having a high xyloglucan-degrading activity may be of particular use for degradations of cell wall material having a high xyloglucan content, for instance in the wine and fruit industry, for pectin-extraction and for removal of hemicelluloses from textile fibres.
The object of the invention is to provide novel endoglucanases exhibiting useful substrate specificities and a method for producing the endoglucanases in a better yield and higher purity than hitherto possible. A further object is to provide novel products, wherein the proportion of the endo-.beta.-1,4-glucanase is either increased or decreased relative to the proportion in the original product. The endoglucanases and the novel products of the invention, whether alone or in combination with other enzymes may be used for the degradation of plant cell wall tissue.